Provides a format independent interface for writing images to files or other devices. More...

Public Types
enum	ImageWriterError

Public Methods
	QImageWriter ()

	QImageWriter (const QString &fileName, const QString &format=QString ())

	QImageWriter (QIODevice *device, const QString &format)

	~QImageWriter ()

bool	canWrite () const

int	compression () const

QIODevice *	device () const

ImageWriterError	error () const

QString	errorString () const

QString	fileName () const

QString	format () const

float	gamma () const

bool	optimizedWrite () const

bool	progressiveScanWrite () const

int	quality () const

void	setCompression (int compression)

void	setDevice (QIODevice *device)

void	setFileName (const QString &fileName)

void	setFormat (const QString &format)

void	setGamma (float gamma)

void	setOptimizedWrite (bool optimize)

void	setProgressiveScanWrite (bool progressive)

void	setQuality (int quality)

void	setSubType (const QByteArray &type)

void	setText (const QString &key, const QString &text)

void	setTransformation (QImageIOHandler::Transformations transform)

QByteArray	subType () const

QList< QByteArray >	supportedSubTypes () const

bool	supportsOption (QImageIOHandler::ImageOption option) const

QImageIOHandler::Transformations	transformation () const

bool	write (const QImage &image)

Static Public Methods
static QList< QString >	supportedImageFormats ()

static QList< QString >	supportedMimeTypes ()

Detailed Description

The QImageWriter class provides a format independent interface for writing images to files or other devices. QImageWriter supports setting format specific options, such as the gamma level, compression level and quality, prior to storing the image. If you do not need such options, you can use QImage::save() or QPixmap::save() instead.

To store an image, you start by constructing a QImageWriter object. Pass either a file name or a device pointer, and the image format to QImageWriter's constructor. You can then set several options, such as the gamma level (by calling setGamma()) and quality (by calling setQuality()). canWrite() returns true if QImageWriter can write the image (i.e., the image format is supported and the device is open for writing). Call write() to write the image to the device.

If any error occurs when writing the image, write() will return false. You can then call error() to find the type of error that occurred, or errorString() to get a human readable description of what went wrong.

Call supportedImageFormats() for a list of formats that QImageWriter can write. QImageWriter supports all built-in image formats, in addition to any image format plugins that support writing.

See also: QImageReader, QImageIOHandler, QImageIOPlugin

Member Enumeration Documentation

enum QImageWriter::ImageWriterError

This enum describes errors that can occur when writing images with QImageWriter.

Constant	Value	Description
`QImageWriter::DeviceError`	`1`	QImageWriter encountered a device error when writing the image data. Consult your device for more details on what went wrong.
`QImageWriter::UnsupportedFormatError`	`2`	CopperSpice does not support the requested image format.
`QImageWriter::UnknownError`	`0`	An unknown error occurred. If you get this value after calling write(), it is most likely caused by a bug in QImageWriter.

Constructor & Destructor Documentation

QImageWriter::QImageWriter ( )

Constructs an empty QImageWriter object. Before writing, you must call setFormat() to set an image format, then setDevice() or setFileName().

QImageWriter::QImageWriter	(	QIODevice *	device,
		const QString &	format
	)

explicit

Constructs a QImageWriter object using the given device and image format.

QImageWriter::QImageWriter	(	const QString &	fileName,
		const QString &	format = `QString()`
	)

explicit

Constructs a QImageWriter objects that will write to a file with the name fileName, using the image format format. If format is empty, QImageWriter will detect the image format by inspecting the extension of fileName.

QImageWriter::~QImageWriter ( )

Destructs the QImageWriter object.

Method Documentation

bool QImageWriter::canWrite ( ) const

Returns true if QImageWriter can write the image; i.e., the image format is supported and the assigned device is open for reading.

See also: write(), setDevice(), setFormat()

int QImageWriter::compression ( ) const

Returns the compression of the image.

See also: setCompression()

QIODevice * QImageWriter::device ( ) const

Returns the device currently assigned to QImageWriter or a nullptr if no device has been assigned.

See also: setDevice()

ImageWriterError QImageWriter::error ( ) const

Returns the type of error that last occurred.

See also: ImageWriterError, errorString()

QString QImageWriter::errorString ( ) const

Returns a human readable description of the last error that occurred.

See also: error()

QString QImageWriter::fileName ( ) const

If the currently assigned device is a QFile, or if setFileName() has been called, this function returns the name of the file QImageWriter writes to. Otherwise (i.e., if no device has been assigned or the device is not a QFile), an empty QString is returned.

See also: setFileName(), setDevice()

QString QImageWriter::format ( ) const

Returns the format QImageWriter uses for writing images.

See also: setFormat()

float QImageWriter::gamma ( ) const

Returns the gamma level of the image.

See also: setGamma()

bool QImageWriter::optimizedWrite ( ) const

Returns whether optimization has been turned on for writing the image.

See also: setOptimizedWrite()

bool QImageWriter::progressiveScanWrite ( ) const

Returns whether the image should be written as a progressive image.

See also: setProgressiveScanWrite()

int QImageWriter::quality ( ) const

Returns the quality level of the image.

See also: setQuality()

void QImageWriter::setCompression ( int compression )

This is an image format specific function that set the compression of an image. For image formats that do not support setting the compression, this value is ignored.

The value range of compression depends on the image format. For example, the "tiff" format supports two values, 0(no compression) and 1(LZW-compression).

See also: compression()

void QImageWriter::setDevice ( QIODevice * device )

Sets QImageWriter's device to device. If a device has already been set, the old device is removed from QImageWriter and is otherwise left unchanged.

If the device is not already open, QImageWriter will attempt to open the device in QIODevice::WriteOnly mode by calling open(). Note that this does not work for certain devices, such as QProcess, QTcpSocket and QUdpSocket, where more logic is required to open the device.

See also: device(), setFileName()

void QImageWriter::setFileName ( const QString & fileName )

Sets the file name of QImageWriter to fileName. Internally, QImageWriter will create a QFile and open it in QIODevice::WriteOnly mode, and use this file when writing images.

See also: fileName(), setDevice()

void QImageWriter::setFormat ( const QString & format )

Sets the format QImageWriter will use when writing images, to format. The format is a case insensitive text string. You can call supportedImageFormats() for the full list of formats QImageWriter supports.

QImageWriter writer;

writer.setFormat("png"); // same as writer.setFormat("PNG");

See also: format()

void QImageWriter::setGamma ( float gamma )

This is an image format specific function that sets the gamma level of the image to gamma. For image formats that do not support setting the gamma level, this value is ignored.

The value range of gamma depends on the image format. For example, the "png" format supports a gamma range from 0.0 to 1.0.

See also: gamma(), quality()

void QImageWriter::setOptimizedWrite ( bool optimize )

This is an image format-specific method which sets the optimize flag to optimize when writing images. For image formats that do not support setting an optimize flag, this value is ignored.

The default value for optimize is false.

See also: optimizedWrite()

void QImageWriter::setProgressiveScanWrite ( bool progressive )

This is an image format-specific method which sets the value of the progressive scanning flag to progressive when writing images. For image formats that do not support setting a progressive scan flag, this value is ignored.

The default is false.

See also: progressiveScanWrite()

void QImageWriter::setQuality ( int quality )

This is an image format specific function that sets the quality level of the image to quality. For image formats that do not support setting the quality, this value is ignored.

The value range of quality depends on the image format. For example, the "jpeg" format supports a quality range from 0 (low quality, high compression) to 100 (high quality, low compression).

See also: quality()

void QImageWriter::setSubType ( const QByteArray & type )

This is an image format specific function that sets the subtype of the image to type. Subtype can be used by a handler to determine which format it should use while saving the image.

The following is an example to save an image in DDS format with A8R8G8R8 subtype.

QImageWriter writer("some/image.dds");
 
if (writer.supportsOption(QImageIOHandler::SubType)) {
   writer.setSubType("A8R8G8B8");
}
 
writer.write(image);

See also: subType()

void QImageWriter::setText	(	const QString &	key,
		const QString &	text
	)

Sets the image text associated with the given key to text. This is useful for storing copyright information or other information about the image.

To store a single block of data such as a comment, pass an empty key or use a generic key like "Description". The key and text will be embedded into the image data after calling write(). Support for this option is implemented through QImageIOHandler::Description.

QImage image("some/image.jpeg");
QImageWriter writer("images/outimage.png", "png");
 
writer.setText("Author", "John Smith");
writer.write(image);

See also: QImage::setText(), QImageReader::text()

void QImageWriter::setTransformation ( QImageIOHandler::Transformations transform )

Sets the image transformations metadata including orientation to transform. If transformation metadata is not supported by the image format the transform is applied before writing.

See also: transformation(), write()

QByteArray QImageWriter::subType ( ) const

Returns the subtype of the image.

See also: setSubType()

QList< QString > QImageWriter::supportedImageFormats ( )

static

Returns the list of image formats supported by QImageWriter. The QApplication instance must be created before this method is called. Reading and writing SVG files is supported through the CsSvg library.

The following formats are currently supported.

Format	Description
BMP	Windows Bitmap
JPG	Joint Photographic Experts Group
JPEG	Joint Photographic Experts Group
PNG	Portable Network Graphics
PPM	Portable Pixmap
TIFF	Tagged Image File Format
XBM	X11 Bitmap
XPM	X11 Pixmap

See also: setFormat(), QImageReader::supportedImageFormats(), QImageIOPlugin

QList< QString > QImageWriter::supportedMimeTypes ( )

static

Returns the list of MIME types supported by QImageWriter. The QApplication instance must be created before this method is called.

See also: supportedImageFormats(), QImageReader::supportedMimeTypes()

QList< QByteArray > QImageWriter::supportedSubTypes ( ) const

Returns the list of subtypes supported by an image.

See also: setSubType()

bool QImageWriter::supportsOption ( QImageIOHandler::ImageOption option ) const

Returns true if the writer supports option, otherwise returns false.

Different image formats support different options. Call this method to determine whether a certain option is supported by the current format. For example, the PNG format allows you to embed text into the image's metadata (see text()).

Options can be tested after the writer has been associated with a format.

QImageWriter writer(fileName);
 
if (writer.supportsOption(QImageIOHandler::Description)) {
 writer.setText("Author", "John Smith");
}

See also: QImageReader::supportsOption(), setFormat()

QImageIOHandler::Transformations QImageWriter::transformation ( ) const

Returns the transformation and orientation the image has been set to written with.

See also: setTransformation()

bool QImageWriter::write ( const QImage & image )

Writes the image to the assigned device or file name. Returns true on success, otherwise returns false. If the operation fails, you can call error() to find the type of error that occurred, or errorString() to get a human readable description of the error.

See also: canWrite(), error(), errorString()

Public Types

Public Methods

Static Public Methods

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Method Documentation